Redox-active Azobenzene Conjugated Molecules:Synthesized And Photochemical Properties

The photochromic molecules have become a hot area of research in recent years,due to their wide applications in molecular switches and optical memory.The design and synthesis of photochromic molecules with excellent perfonnance have important scientific value;however,it is also facing major challenges.Azobenzene derivatives,probably the most widely applicable photoisomerization molecules,are well-known for their high synthetic versatility and excellent photochemical properties.Organometallic azobenzene derivatives have received much more attention due to the combination of the photoswitchable azobenene group with the optical,electrochemical,magnetic and biological properties of the metal complexes.In this paper,we design and synthesis a series of azobenzene derivatives with the redox-active center such as ferrocene,ferrocenylethynyl and 4,4'-dimethoxy-triphenylamine.and their characterization,electrochemistry and photochromic properties will be explored.The main contents include three aspects:1.The introduction of ferrocenylethynyl group into the azobenzene system can regulate the photoisomerization properties of ferocenyl azobenzene derivatives without changing the main structure of f-unctional groups.Five ferrocenylethynyl-terminated azobenzene derivatives were synthesized and confimed by NMR,MS and elemental analysis.Their electrochemical and photochemical properties were characterized by electrochemistry,UV-Vis spectroscopy and other methods.The effect of position isomerism and the number of ferrocenylethynyl moiety on the properties of azobenzene was discussed.UV-Vis spectroscopy and spectroelectrochemistry studies showed that a metal to ligand charge transfer(MLCT)band was appeared in the visible region of these compounds,and large MLCT components are in the visible region in para-ferrocenylethynyl substituted derivatives comparing to the meta isomers.Compound 13 exhibits excellent fatigue resistance and reversibility upon several reversible isomerization cycles.make it to be a potential molecular switch.2.The electronic communication in D-?-A type azobenzene was enhanced owing to the high degree of polarization in the molecular,which probably affected photochromic properties.A series of push-pull ferrocenyl or ferrocenylethynyl azobenzenes was synthesized,and their photoisomerization properties were described.The photoisomerization properties of D-?-A type para-ferrocenylethynyl azobenzene are significant difference from that in D-?-A type para-ferrocenyl azobenzene.Compared to the D-? type mata-ferrocenyl(ethynyl)azobenzenes,the photoisomerization properties of D-?-A type mata-ferrocenyl(ethynyl)azobenzene are significantly improved.3.4,4'-dimethoxy-tri phenyl amine substituted azobenzene derivatives with ethynyl-bridging chain were synthesized.Electrochemistry and photoisomerization properties were described as well as the different from that of corresponding ferrocenylethynyl azobenzenes.Electrochemical and spectroelectrochemistry studies indicate that these compounds have excellent redox properties.Significant spectra change upon the process of redox makes these compounds have potential applications of electrochemical switching.Photoisomerization studies showed that these compounds have fast photoisomerization rate due to the higher photoisomerization quantum yield,which is an order of magnitude larger than that of ferrocenyl(ethynyl)azobenzenes.